Archives of Sexual Behavior

, Volume 32, Issue 1, pp 23–28 | Cite as

Finger-Length Ratios in Female Monozygotic Twins Discordant for Sexual Orientation

  • Lynn S. HallEmail author
  • Craig T. Love


The second to fourth finger digit ratio (2D:4D ratio) is a sex-dimorphic characteristic in humans that may reflect relative levels of first trimester prenatal sex hormones. Low interdigital ratio has been associated with high levels of androgens. It has been reported in unrelated women that low 2D:4D ratio is associated with lesbian sexual orientation, but because of the nature of those samples, it was not possible to conclude whether lower ratio (and hypothetically, higher androgen levels) in lesbians are due to differences in genetics as opposed to differences in environment. To test the hypothesis that low 2D:4D in lesbians is due to differences in environment, interdigital ratio data were analyzed in a sample of female monozygotic (MZ) twins discordant for sexual orientation (1 twin was lesbian, the other was heterosexual; n = 7 pairs). A control group of female MZ twins concordant for sexual orientation (both twins were lesbian) was used as a comparison (n = 5 pairs). In the twins discordant for sexual orientation, the lesbian twins had significantly lower 2D:4D ratios on both the right and left hands than their heterosexual cotwins. There were no significant differences for either hand in the twins concordant for sexual orientation. Because MZ twins share virtually the same genes, differences in 2D:4D ratio suggest that low 2D:4D ratio is a result of differences in prenatal environment.

lesbian monozygotic twins interdigital ratio sexual orientation 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Allen, L. S., & Gorski, R. A. (1992). Sexual orientation and the size of the anterior commissure in the human brain. Proceedings of the National Academy of Sciences of the United States of America, 89, 7199–7202.Google Scholar
  2. Austin, E. J., Manning, J. T., McInroy, K., & Mathews, E. (in press). An investigation of the associations between personality, cognitive ability and digit ratio. Personality and Individual Differences.Google Scholar
  3. Babler, W. J. (1991). Embyological development of epidermal ridges and their configurations. In C. C. Plato, R. M. Garruto, & B. A. Schaumann (Eds.), Dermatoglyphics: Science in transition (pp. 95–112). New York: Wiley.Google Scholar
  4. Bailey, J. M., Pillard, R. C., Neale, M. C., & Agyei, Y. (1993). Heritable factors influence sexual orientation in women. Archives of General Psychiatry, 50, 217–223.Google Scholar
  5. Blanchard, R. (1997). Birth order and sibling sex ratio in homosexual and heterosexual males and females. Annual Review of Sex Research, 8, 27–67.Google Scholar
  6. Bracha, H. S., Torrey, E. F., Gottesman, I. I., Bigelow, L. B., & Cunniff, C. (1992). Second trimester markers of fetal size in schizophrenia: A study of monozygotic twins. American Journal of Psychiatry, 149, 1355–1361.Google Scholar
  7. Brown, W. M., Hines, M., Fane, B., & Breedlove, S. M. (in press). Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia. Hormones and Behavior.Google Scholar
  8. Brown, W. M., Finn, C. J., Cooke, B. M., & Breedlove, S. M. (2002). Differences in finger length ratios between self-identified “butch” and “femme” lesbians. Archives of Sexual Behavior, 31, 117–121.Google Scholar
  9. Byne, W., Tobet, S., Mattice, L. A., Lasco, M. S., Kemether, E., Edgar, M. A., et al. (2001). The interstitial nuclei of the human anterior hypothalamus: An investigation of variation with sex, sexual orientation, and HIV status. Hormones and Behavior, 40, 86–92.Google Scholar
  10. Cederlof, R., Friberg, L., Johnson, E., & Kaij, L. (1961). Studies on similarity diagnosis in twins with the aid of mailed questionnaires. Acta Genetica Statistica Medicologica, 11, 338–362.Google Scholar
  11. Garn, S. M., Burdi, A. R., Babler, W. J., & Stinson, S. (1975). Early prenatal attainment of adult metacarpal-phalangeal rankings and proportions. American Journal of Physical Anthropology, 43, 327–332.Google Scholar
  12. George, R. (1930). Human finger types. Anatomical Record, 46, 199–204.Google Scholar
  13. Hall, L. S. (2000a). Dermatoglyphic analysis of monozygotic twins discordant for sexual orientation. In N. M. Durham, K. M. Fox, & C. C. Plato (Eds.), The state of dermatoglyphics: The science of finger and palm prints (pp. 123–165). Lewiston, NY: Edwin Mellen.Google Scholar
  14. Hall, L. S. (2000b). Dermatoglyphic analysis of total finger count in female monozygotic twins discordant for sexual orientation. Journal of Sex Research, 37, 315–320.Google Scholar
  15. Hall, L. S. (2001a, Fall). Assessing 2nd to 4th interdigital ratio using inked prints. Newsletter of the American Dermatoglyphics Association, 24, 17–24.Google Scholar
  16. Hall, L. S. (2001b). A relationship between markers of 1st trimester testosterone levels and drinking scores in males [Abstract]. Alcoholism: Clinical and Experimental Research 25, 151.Google Scholar
  17. Hershberger, S. L. (1997). A twin registry study of male and female sexual orientation. Journal of Sex Research 34, 212–222.Google Scholar
  18. Kinsey, A. C., Pomeroy, W. B., & Martin, C. E. (1948). Sexual behavior in the human male. Philadelphia: Saunders.Google Scholar
  19. Klein, F., Sepekoff, B., & Wolf, T. J. (1985). Sexual orientation: A multi variable dynamic process. Journal of Homosexuality 11, 35–49.Google Scholar
  20. LeVay, S. (1991). A difference in hypothalamic structure between heterosexual and homosexual men. Science, 253, 1034–1037.Google Scholar
  21. LeVay, S. (1996). Queer science. Cambridge, MA: MIT Press.Google Scholar
  22. Lutchmaya, S., Baron-Cohen, S., Raggatt, P., Knickermeyer, R., & Manning, J. T. (2002). 2nd to 4th digit ratios, fetal testosterone and estradiol. Manuscript submitted for publication.Google Scholar
  23. Manning, J. T. (2001). Re: The ratio of 2nd to 4th digit length and age at presentation of breast cancer: A link with prenatal oestrogen? The Breast, 10, 355–357.Google Scholar
  24. Manning, J. T. (2002). Digit ratio: A pointer to fertility, behavior, and health. New Brunswick, NJ: Rutgers University Press.Google Scholar
  25. Manning, J. T, & Bundred, P. E. (2000). The ratio of 2nd to 4th digit length: A new predictor of disease predisposition? Medical Hypotheses, 54, 855–857.Google Scholar
  26. Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to 4th digit length: A predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen. Human Reproduction, 13, 3000–3004.Google Scholar
  27. Manning, J. T., & Taylor, R. P. (2001). Second to fourth digit ratio and male ability in sport: Implications for sexual selection in humans. Evolution and Human Behavior, 22, 61–69.Google Scholar
  28. Manning, J. T., Trivers, R. L., Singh, D., & Thornhill, R. (1999). The mystery of female beauty. Nature, 399, 214–215.Google Scholar
  29. Martin, S., Manning, J. T., Trivers, R. L., Singh, D., Venkatramana, P., Henzi, P., et al. (2001, June). 2nd to 4th digit ratio and family size in England, Jamaica, India and South Africa. Paper presented at the annual meeting of the Human Behavior and Evolution Society, London, England.Google Scholar
  30. McFadden, D. (2002). Masculinization effects in the auditory system. Archives of Sexual Behavior, 31, 93–105.Google Scholar
  31. McFadden, D., & Champlin, C. A. (2000). Comparison of the auditory evoked potentials in heterosexual, homosexual, and bisexual males and females. Journal of the Association of Research in Otolaryncology, 1, 89–99.Google Scholar
  32. McFadden, D., & Pasanen, E. G. (1998). Comparison of the auditory systems of heterosexuals and homosexuals: Click-evoked otoacoustic emissions. Proceedings of the National Academy of Sciences of the United States of America, 95, 2709–2713.Google Scholar
  33. Nichols, R. C., & Bilbro, W.C. (1966). The diagnosis of twin zygosity. Acta Genetica Statistica Medicologica, 16, 265–275.Google Scholar
  34. Phelps, V. R. (1952). Relative index finger length as a sex-influenced trait in man. American Journal of Human Genetics 4, 72–89.Google Scholar
  35. Robinson, S. J., & Manning, J. T. (2000). The ratio of 2nd to 4th digit length and male homosexuality. Evolution and Human Behavior, 21, 333–345.Google Scholar
  36. Sorenson-Jamison, C. S., Meier, R. J., & Campbell, B. C. (1993). Dermatoglyphic asymmetry and testosterone levels in normal males. American Journal of Physical Anthropology, 90, 185–198.Google Scholar
  37. Tortorice, J. (2001, June). Gender identity, sexual orientation, and second-to-fourth digit ratio in females. Paper presented at the annual meeting of the Human Behavior and Evolution Society, London, England.Google Scholar
  38. Tortorice, J. (2002). Independent development of gender identity and sexual orientation in females as reflected in second-to-fourth digit ratios. Manuscript submitted for publication.Google Scholar
  39. Williams, T. J., Pepitone, M. E., Christensen, S. E., Cooke, B. M., Huberman, A. D., Breedlove, N. J., et al. (2000). Finger length ratios and sexual orientation. Nature, 404, 455–456.Google Scholar

Copyright information

© Plenum Publishing Corporation 2003

Authors and Affiliations

  1. 1.Department of Psychiatry, School of MedicineNew York UniversityNew York
  2. 2.Center for Alcohol and Addiction StudiesBrown UniversityProvidence

Personalised recommendations